Electrostatic recording with interchangeable stencils



May 23, 1967v T. E. BYRD 3,321,758

ELECTROSTATIC RECORDING WITH INTERCHANGEABLE STENCILS Filed May 12, 1960 4 Sheets-Sheet 1 INVENTOR.

THEODORE E. BYRD BY AGENT May 23, 1967 T.'E. BYRD 3,321,763

ELECTROSTATIC RECORDING WITH INTERCHANGEABLE STENCILS Filed May 12. 1960 F fg. /2 I85 2??? 25 4 5 6 /3 OW N ER INVENTOR.

THEODORE E. BYRD AGENT 4 Sheets-Sheet 4 I operation.

United States Patent 3,321,768 ELECTROSTATIC RECORDING WITH INTERCHANGEABLE STENCILS Theodore E. Byrd, Philadelphia, Pa., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed May 12, 1960, Ser. No. 28,670 3 Claims. (Cl. 346-74) This invention pertains to the reproduction of symbols by electrostatic means, particularly to printing.

It is known in the art to produce a pattern of electric charges of the shape of a given symbol or letter or character by employing as a source of an electrical discharge producing such a pattern an electrode of the same general shape as the symbols in whose image a charge pattern is to be established. This method, while it is obviously fairly proof against unexpected metamorphoses of one symbol into another, has the disadvantage that the formation of symbols in metal or equivalent material is required, necessitating a somewhat expensive operation; and, if a whole font is to be produced by coining, rather expensive tooling is needed. Another disadvantage is the requirement to mount the character representing electrodes on a carrier for movement past the printing positions. There exists a further inconvenience that a given font, once installed in suitable apparatus for its employment, can be exchanged for another only with a moderate expenditure of time and labor, such as to preclude any interchange of type faces or symbol assortments during the progress of a recording My invention teaches a rapid and inexpensive way of assigning to each of a multiplicitycf identical electrodes the ability to produce any particular one of a multiplicity of symbols; and of altering this assignment at will to a new assignment of arbitrarily different symbols, the change being sulficiently simple and rapid so that it is feasible to accomplish it during the making of a single series of records, by automatic means if desired.

I have found that it is possible to produce a nondisruptive electrical discharge having a cross-section of shape corresponding to a desired symbol by employing a baflie or mask interposed in the path of a discharge from a simple electrode of round or other gross cross section, the bafile being pierced with an aperture shaped like the symbol in whose image it is desired to form the electrical discharge. If a multiplicity of electrodes is to be employed for the formation of a number of different symbols, the mask may be a single one adapted to present to each electrode of the multiplicity the aperture required to form a discharge corresponding to the symbol to be associated with that electrode; and the entire font of symbols may be altered at once by replacing a first mask by a second one.

On the other hand, if it is desired to employ electrostatic recording at a relatively slow rate compatible with the use of mechanical motion of a mask, then a single electrode may be employed as a source of the shaped discharge, and means may be provided for presenting various mask apertures before the single electrode according as it is desired to record different symbols. These mask apertures may be all located in a unitary mask base, or they may be separate, according to the mechanical structure most convenient for meeting the exigencies of the application. A rotating hollow cylinder or disk of apertures may be employed conveniently, since such cylinder or disk may be adapted for very high-speed rotation because of its relative lightness (since it need not carry any electrodes) and the extreme rapidity of the electrostatic recording process makes it possible to make a record during a time interval when the 3,321,768 Patented May 23, 1967 desired mask moves only an imperceptible distance in its path across the record medium. Thus it is feasible to achieve the relative simplicity of a recording system .whose symbols are formed by simple geometry, rather tively simple and inexpensive apparatus.

Other important objects and advantages of my inven tion will appear in the course of'the detailed specification which follows.

For the better understanding and explanation of my invention, I provide figures of drawing as follows:

'FIG. 1 represents a discharge from an unmasked electrode;

FIG. 2 represents the electrode of FIG. 1 masked according to my invention, and the discharge shape resulting from such masking;

FIG. 3 represents a fixed electrode with a movable mask disk arranged to cause the electrostatic recording of various symbols depending upon the disk position;

FIG. 4 represents a disk for recording a different set of symbols interchangeable with that of FIG. 3;

FIG. 5 represents a printing station suitable for a page printer with the fonts provided by a fixed mask;

FIG. 6 represents a mask and associated electrodes suitable for use in the apparatus of FIG. 5;

FIG. 7 represents page printing apparatus employing the principles of my invention;

FIG. 8 represents an additional partly sectional view of a detail of FIG. 7;

FIG. 9 represents an alternate formof page printing apparatus employing the principles of my invention; FIG. 10 represents an additional partly sectional view of a detail of FIG. 9; FIG. 11 represents a detail of FIGS. 9, 10, and 12;

FIG. 12 represents an alternate form of printing station for a page printer embodying the principles of my invention; and v I FIG. 13 represents the flexible strip mask detail of FIG. 12.

In FIG. 1, a conventional round or cylindrically shaped electrode 11 is represented as connected by conductor 12 to a current pulse source 13 having a grounded return. A grounded conductive anvil or back electrode 15 is opposed to electrode 11. The space between electrodes 11 and 15 provides a gap for receiving a dielectric record medium 14, which may but need not necessarily have an electrically conductive lower surface or reverse. An electrical pulse of sufiicient voltage from source 13 will produce a noiseless non-disruptive discharge through the ambient air or other gas and will produce on the upper surface of medium 14 an invisible pattern of electrical charges outlined bydashed circle 16. (For clarity, mechanical supports are omitted in all figures).

If the same elements represented in FIG. 1 are modified as represented in FIG. 2. by the interposition between electrode 11 and medium 14 of a mask 18 provided with a shaped aperture 19, the electrical discharge from electrode 11 will be so restricted in general accordance with the shape of the aperture 19 that there will be deposited on the non-conductive upper surface of medium 14 an invisible electric charge pattern delineated by the dashed lines 17, of the same general shape as the aperture 19. The mask 18 may be electrically non-conductive, or, if

electrically conductive, it should preferably be maintained at a potential intermediate between ground and the pulse potential of electrode 11. The limit of potential of mask 18 is that it should not be so close to the potential of the electrode 11 that there will be danger of discharges from mask 18 to medium 14, nor beyond ground potential to such an extent that it tends to capture charges and prevent them from reaching medium 14. The material of mask 18 should not be rapidly eroded by electrical discharges; therefore materials such as ceramics or stable mineral substances are suitable for such use.

FIG. 3 represents a recording device employing a single electrode 11 for recording on medium 14 any selected ones of a variety of numerals outlined by apertures 191 in mask 181. Mask 181 is supported by a central shaft 20 and is rotatable with this shaft by drive means 21, such as an electric motor, but represented only by dashes because concealed by mask 181. Drive means 21 is connected by channel 22 to control unit and data source 131, to which electrode 11 is represented connected by conductor 12. Control unit and data source 131 is represented only by a rectangle since in actual practice it may be composed of a wide variety of devices and circuits, the existing art being very voluminous. The control unit and data source 131 is required to be so designed that, in accordance with the data to be printed, it either senses via channel 22 the position of the mask 181 if drive means 21 is rotating independently, or it controls drive means 21 via channel 22; in either case, when the aperture 191 appropriate to the information to be recorded is in position under electrode 11, control unit and data source 131 applies to electrodes 11 via conductor 12 a pulse which causes an electrical discharge to occur from electrode 11 through the aperture 191 of mask 181 and thus produce on the obverse of medium 14 a pattern of electrical charges similar in shape to the shape of the aperture 191.

Because the time for production of a charge pattern as described may be less than a microsecond, noticeable smearing of the record by motion of the medium through an appreciable distance during the making of the record will not occur. However, it is necessary that the discharges for recording successive charge patterns occur at the times corresponding to the location under the electrode 11 of the desired portions of the medium 14. Therefore drive means 24, which rotates advance roll 23 to advance medium 14 to the right of the figure, as indicated by the arrow, is represented as connected by channel 25 to control unit and data source 131. In this instance, also, either drive means 24 may operate at constant speed and the amount of its advance may be indicated via channel 25 to unit 131, or unit 131 may be provided with the capability of controlling drive means 24 via channel 25. In either case, the operation of control unit and data source is so coordinated with the motion of medium 14 and the rotation of mask 181 that a recording electrical pulse is applied to electrode 11 only at the time when the proper aperture 191 is located over the proper part of the medium 14. The electric charges 17 deposited in patterns on the obverse of medium 14 may be rendered visible by standard techniques of development, the means not being here represented.

FIG. 4 represents a mask 182 containing apertures 192. This mask may be interchanged with the mask 181 represented in FIGURE 3, to produce a completely new and different font of symbols to be recorded. This representation is for the purpose of teaching how readily a complete font of symbols may be exchanged by the change of a single mechanical piece, in the practice of my invention.

FIG. represents a printing station and auxiliaries adapted for use as a page printer. A roll 3-1 is represented as carrying a supply of dielectric medium 141 which is rolled up, by drive means not represented, on roll 33. In its course, medium 141 passes over a grounded anvil 151 which is at least as wide as the medium 141 and as long in the direction of advance of the medium as the length of a column consisting of the entire font of symbols. A font mask 183 is placed adjacent to the upper surface (visible directly in the figure) of medium 141. FIG. 6 is a representation of a part of mask 183 and indicates that for each column width of the page to be printed, mask 183 carries an entire font of shaped apertures 193. Adjacent to the mask 183 is an array of similarly shaped insulated electrodes 111 (partly represented in FIG. 6) of which each electrode is connected by a separate one of conductors 121 to control unit and data source 132. Control unit and data source 132 operates, in accordance with the data to be recorded, to apply to the appropriate ones of conductors 121 current pulses which cause the deposition of patterns of electric charges upon medium 141. It is apparent that the particular stage of its progress from one roll to another at which a given area of medium 141 will receive a stored charge depends upon the particular symbol to be recorded, an A being recorded first in the particular example here represented. For completeness of the representation, rectangle 32 is included to indicate the location of the developing and fixing apparatus in relation to the printing station and the direction of motion of the medium 141. Electric charge patterns 117, invisible, are represented by dotted lines, while the developed and fixed symbols 34 are represented approximately as they would appear.

It is evident that, given a printing station and auxiliaries of the kind represented in FIG. 5, a completely new font of symbols may be provided very readily by replacing mask 183 by a new mask provided with apertures corresponding to the new symbols; and that such replacement may be rapid and inexpensive. By contrast, replacement of shaped electrodes would require change of a large number of much smaller parts, susceptible to misalignment, and requiring care in installation to avoid damage to insulation necessary for their operation.

FIGURE 7 represents a page printing apparatus in which a record medium 142 is fed from a supply roll 31 to a takeup roll 33, passing in transit a recording station not individually numbered and a developing station 32, the means driving takeup roll 33 not being indicated, in view of the voluminous art teaching means of driving a shaft rotatingly. A mask 184 is made in the form of a right circular cylinder supported by a hub not numbered upon the shaft of a motor 241. The axis of rotation of mask 184 (and of the shaft of motor 241) is parallel to the surface of medium 142 and to a line of symbols to be printed. For each character position in the line across the page, there is pierced through the mask 184 in a plane including the point along the axis of the cylinder corresponding to the character position and around the periphery of the cylinder a font of the characters to be recorded selectively at that position.

A conventional full font would consist of letters, arabic numerals, and punctuation marks; but for particular purposes certain character positions might be restricted to numerals, others to letters, and so on. A character or symbol might, in particular instances, be composed of a number of letters, signs, and numerals in various com binations, such as 10% net. Motor 241 is specified as being capable, in some one of the many ways known to the art of the present date, of being rotated to specific angular position, which will bring a particular symbol aperture in nearest proximity to the surface of medium 142, in response to a control signal transmitted to it via channel 42 from information source and control unit 133. Channel 42 may be cable if it is subject to such mechanical stress as requires such construction; or it may be more conventional electrical conductor or conductors (it is represented as a single conductor with ground return); or it may be any channel of control or information, including a modulated light source and a photocell receiver, or a carrier channel, or any other device falling within the well defined sense of the word channel in the communications and electronics arts. The relation between the angular position of motor 241 and information source and control unit 133 is bascially required only to be such that the relation between the angular positionof motor 241 and mask 184 is so correlated with the functioning of information source and control unit 133 that a recording electrical discharge from recording electrode 112 occurs at a time when the desired symbol of mask 184 is interposed in the path of the recording discharge to the surface of medium 142. This end may be achieved either by caus ing the .information source and control unit 133 to deter mine the angular position of the shaft of motor 241 and of mask 184; or by allowing motor 241 and mask 184 to rotate freely at a given speed, and causing signals indicative of the angular position to be transmitted over channel 42 to information source and control unit 133 and cause the timing of the electrical discharge from recording electrode 112 to occur only at the desired time. Both methods are identical in the result achieved, and are alternatives which, so far as the teachings of my invention is concerned, differ only in picayune degree.

Since the embodiment of FIGURE 7 represents only a single recording electrode 112, insulated by insulator 45 (here represented as a conventional stand-off insulator of the kind well known in the electronics art and available from, inter alia, E. F. Johnson Company, Waseca, Minnesota), it is necessary to provide some means for recording separately in desired succession at the various character positions along a given line across record medium 142. p

This is achieved by providing behind medium 142 a number of separate and mutally insulated electrodes, sometimes designated as anvils, each such one of anvils 152 being separately connected via conductors 44 to selection pulse source 35. Record medium 142, for this purpose, should not be provided with an electrically conductive backing. Recording pulse source 36 is so de signed that it provides to recording electrode 112 via conductor 123 an electrical pulse of insufficient potential with respect to the unexcited potential of anvils 152 to produce a recording discharge in the ambient atmosphere adjacent to the surface of record medium 142. Anvil selection pulse source 35 is designed to be capable, in compliance with control signals from information source and control unit 133, transmitted via channel 43, of maintaining at normal unexcited potential all of anvils 152 except one selected anvil, which is excited to a potential opposite in sign to that of the recording pulse, and insufficient in magnitude to produce alone an electrical field of recording intensity in the gap between the recording electrode 112 and the record medium 142, but capable of producing such a field of recording intensity when its effect is combined with the effect of a recording pulse applied to recording electrode 112.

The separation of anvils 152, as they are supported by insulator 46, is represented in FIG. 8, together with the relation of record medium 142 (which is represented in section) and of insulator 45, recording electrode 112, conductor 123, mask 184, motor 241, and channel 42 with respect to each other (the insulation 46 supporting anvils 152 is not represented in FIG. 7). This basic method of producing selective electrical recording at various positions along a line of recording is thesubject of United States Patent No. 2,919,171, issued Dec.-29, 1959, to the assignee of the present application, entitled, Page Printing Apparatus.

In brief summary, the operation of the apparatus represented in FIG. 7 is as follows. The apparatus is assumed to have been set in operation, including the starting of the means driving take-up roll 33 so that the medium 142 is advanced from supply roll 31 past the recording station including mask 1 84, past the developing station 32, andto roll 33. In accordance with information already stored in it, information source and control unit 133, at a time when the desired symbol perforation on mask 184 is nearest opposed to record medium 142, causes a recording pulse to be applied by recording pulse source 36 to recording electrode 112, and simultaneously causes an anvil selection pulse to be applied by anvil selection pulse source 35 to the selected anvil 152, causing a recording discharge to occur and produce on the surface of record medium 142 a pattern of electric charges in the shape of the selected symbol at the selected location. By repetition of this procedure, lines of symbol patterns may be pro.- duced, as represented by the dotted lines 172. Passage of these invisible charge patterns through the developing station 32 will cause them to be coated with contrasting developing medium and thus rendered visible, as represented by line of symbols 341.

FIGS. 9, 10, and 11 represent apparatus for the application of my invention to a page printer. Record medium 141 may be provided with an electrically conductive backing, since the back electrode or anvil 153 is either one piece or of a multiplicity of electrically conductive pieces electrically connected together, and grounded; it is not necessary to maintain different potentials along different areas of the back of the record medium which are in con tact with the anvil.

The single printing electrode 112 of the apparatus represented in FIG. 7 is replaced by an assembly 113 of electrodes 37 mutually insulated from each other and supported by electrically insulating material 38, all as represented in particular in FIG. 11. Record medium 141 is fed from supply roll 31 past the recording station, the developing station 32, and rolled up on take-up roll 33, which is driven by rotatory or torque-applying means not here shown, precisely as in FIG. 7. Channel 42 is so related to motor. 241 that, at the designers pleasure, it either transmits to motor 241 control signals which cause the shaft of motor 241 and the attached cylindrical mask 184 to assume a directed angular position, or channel 42 may, if the system is so designed, transmit from motor 241 signals indicative of the angular position of the shaft of motor 241 and of cylindrical mask 184.

As was explained in connection with the explanation of FIG. 7, the requisite purpose of synchronizing recording discharges with the desired orientation of mask 184 may be achieved by either scheme. Information source and control unit 134 differs from somewhat similar information source and control unit 133 of FIG. 7 in that unit 134, apart from its relation with motor 241 via channel 42, is in control of selective printing pulse source 361. Selective printing pulse source 361 is separately connected, via conductors 124, which ordinarily will include one conductor for every character space in the line to be printed, to the electrodes 37 of printing head 113.

FIG. 11 shows in detail how the printing electrodes 37, one for each character to be printed in a line, are mounted in insulating material 38 (which may be a molded organic plastic) so that they are commonly aligned and supported, but electrically insulated fromeach other, separate electrical connections being carried out from each electrode 37 as conductors 124.

The functioning of the apparatus of FIG. 9 is like that of FIG. 7, with the difference that the selection of the particular electrode 37 beneath which a discharge is to occur is determined, not by a combination of potentials especially applied to a common printing electrode and to a selected section of the back electrode or anvil, but instead a printing voltage pulse sufficient to produce a recording discharge is applied to a selected individual printing electrode 37, the anvil being at the same potential everywhere behind the record medium 141, preferably at ground. The design of FIG. 9 requires that selective printing pulse source 361 be capable of receiving from information source and control unit 134 control signals or instructions which determine, not only at what time a printing discharge shall occur, but to which of the electrodes 37 the printing or recording'voltage pulse shall be applied.

Apart from this detail, the mode of operation of the apparatus of FIG. 9 is substantially like the mode of operation of the apparatus of FIG. 7. FIG. 10 is a partly sectional view of the relationship to each other of anvil 153, medium 141, and mask 184 with its driving motor 241; only the conductors 124 to printing or recording head or electrode assembly 113 are represented.

FIG. 12 represents a modified application of my invention to a page printer. In this particular apparatus, mask 185 is in the form of a flexible strip, which may be of some electrical-discharge-resistant material such as a fluorinated organic plastic. Mask 185, paltially represented by FIG. 13, which is pierced with the pattern of the various symbols it is desired to record, is wound over two reels or spools 39 and 40, which are supported by and driven by motors 242 and 243, respectively. Motors 242 and 243 are controlled by information source and control unit 135 so that mask 185 is unwound from one reel and wound up on the other of reels 39 and 40 as may be required to locate beneath a chosen one of the electrodes 37 of recording or print head 113 a particular aperture delineating a particular symbol which is to be recorded by an electrical discharge from the chosen one of electrodes 37.

When the mask 185 has been thus properly positioned, selective printing pulse source 361, in compliance with a signal received from information source and control unit 135, applies to the selected one of electrodes 37 a voltage pulse sufiicient to produce a recording discharge -which, shaped by the mask 185, produces on record medium 141 a pattern of electrical charge which, after development by some means such as developing station 32 of FIG. 9, will produce a visible representation of the symbol. It is evident that mask 185, reels 39 and 40 and motors 242 and 243 may, with suitable replacement of information and control unit 134 by 135, replace motor 241 and mask 184 of FIG. 9, and that this will produce an operative page printer employing the particular embodiment represented in FIG. 12.

If the speed of motion of the medium 141 is not sufficiently slow, in FIGS. 9 and 12, to permit the recording of a whole line while the medium 141 moves only a negligible distance, the recorded line will appear skewed. Several artifices may be employed to remedy this difiiculty. First of all, the printing head 113 and the anvil 153 may be skewed with respect to the direction of motion of the medium 141 so that the skew in the direction of motion of medium 141 between successive character recording positions will be equal to the distance that the medium 141 advances between the recording of characters or symbols in such successive character recording positions. Alternatively, the drive means which have been specified as driving take-up roll 33 may be made to function intermittently so that the medium 141 is brought to a complete stop during the time that a given line is being recorded.

It is evident that other mechanical arrangements may be provided for applying the principles of my invention. The masks outlining the symbols to be recorded need not be of the shapes or nature here represented. For example, it is possible to provide a spherical mask mounted in gimbals, and provide servo-type drive for elevation, azimuth, and translation control so that any desired portion of the spherical mask may be interposed between the record medium and the printing electrode, which must, in this case, necessarily be mounted inside the sphere. Alternatively, the mask may assume the form of a helical strip which, by screw-type motion, presents in succession to all the character recording positions of the printing station all the symbols outlined on the mask.

A more elaborate device for applying the principles of my invention may employ the principles of the Linotype machine. Unit masks, each pierced with a single symbol,

in sufficient variety to provide a supply of each symbol, may be stored in a device similar to the Linotype hoppers or bins, and released in succession as required, to form a line of individual masks forming together the line to be recorded. These may be held in a form and employed as a unit to print an entire line at one time by the discharge from a single large electrode (or, preferably, from a number of electrodes interconnected by discharge-stabilizing resistors).

While the material for masks which are to be subject to repeated use should probably be extremely durable, masks which are to be used for purposes involving relatively limited operation during total life may be made of less durable substances. For example, while FIG. 2 has been simplified by representing only a single symbol aperture 19 in mask 18, it is obvious that aperture 19 may actually be a multiplicity of apertures representing an address or similar relatively fixed data; and an address stencil employed as represented may be required to withstand during life only a few hundred uses. It is clear that for such use extreme durability is not required, and an organic material may be employed.

In general terms, my invention may be employed by using a single aperture to shape the discharge from a single electrode, or by using a multiplicity of apertures selectively to shape the discharge from a single electrode, or by employing a single aperture in various locations to shape the discharges from various electrodes. In all these applications the advantage of altering the shape of the discharge without altering the shape of the electrode or disturbing the necessarily Well insulated electrical system will be achieved.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced other than as specifically described and illustrated.

What is claimed is:

1. In an electrostatic recording page printer, the combination comprising: a record medium store; means for advancing a record medium having a charge-retentive obverse from the said store toward a printing station, the said printing station comprising discharge electrode means comprising individual electrodes and backing electrode means aligned with and in proximity to said discharge electrode means to form a gap for receiving said record medium between said discharge and back electrode means for establishing electric charges upon the obverse of said record medium; data source and control means for applying to said discharge electrode means electrical pulses selectively in accordance with data from said data source wherein said pulses are of magnitude and duration such that said electric charges are established on said record medium during a short duration substantially of the order of the pulse width and the discharge is terminated in a time period of the order of within a microsecond; developing and fixing means for rendering the distribution of said electric charges on said record medium permanently visible; apertured mask means movably interposed between said individual electrodes of said discharge electrode means and said record medium so to shape the discharge from said discharge electrode means as to produce on said record medium distributions of electric changes approximately similar in shape to the apertures of said apertured mask means; means to maintain said mask means at a potential to facilitate good discharge intermediate the potential between said individual electrodes of said discharge electrode means when discharge occurs but sufliciently apart from said last-named potential of said individual electrode means so that said mask means will not discharge to said record medium and sufficiently near ground potential such that said mask means will not tend to capture the charges from said individual electrodes of said discharge electrode and prevent them from reaching said record medium.

2. In electrostatic printing apparatus operable in a gaseous ambient atmosphere having a printing station the combination comprising: first electrode means comprising a plurality of substantially cylindrical first electrodes; second electrode means opposed thereto and forming a gap therebetween; means to position each said substantially cylindrical first electrode in substantially normal relationship to said second electrode means such that one end face of each said cylindrical first electrode faces said second electrode means in position to direct an ionizing discharge in a beam from the first electrode end face towards the second electrode means; masking means comprising a sheet of material perforated to form therein a plurality of apertures having the shapes of symbols to be recorded; mask supporting and positioning means to support the said masking means and to movably position the said masking means so that at least one said aperture is located between an electrode of said first electrode means and an opposed electrode of said sec-nd electrode means and in proximity to said cylindrical first electrode to intercept substantially the entire beam with said one aperture in said mask and its surrounding unapertured material; said masking means being adapted to be removable for change in font; medium supporting and positioning means to support a charge-retentive record medium between said aperture and said opposed electrode of said second electrode means and to position such a record medium so that an area thereof which is to receive the record corresponding to the said aperture is located between said aperture and said opposed electrode; and electrical control means to connect selectively individual ones of said substantially cylindrical first electrodes of said first electrode means and said second electrode means to sources of electrical potential, at least one of said sources including electrical pulse means, for applying between said electrode means differences of electrical potential for producing an ionizing electrical discharge in said ambient atmosphere from said first electrode means through said aperture to accordingly selected portions of the surface of a recording medium supported and positioned as herein recited.

3. Electrostatic recording apparatus comprising: in an ambient atmosphere, first electrode means opposed to and forming a gap with second electrode means; said first electrode means comprising a plurality of substantially cylindrical first electrodes; means to support each said substantially cylindrical first electrode in substantially normal axial relationship to said second electrode means such that said first electrodes are aligned with but electrically insulated from each other and an end face of each said cylindrical first electrode faces said second electrode means in position to direct an ionizing discharge in a beam from the first electrode end face towards the second electrode means; masking means comprising a hollow right circular cylinder of electrical discharge-resistant material perforated through the walls thereof to form a regular array or pattern of apertures of symbols to be recorded; mounting and rotating means for movably mounting said circular cylinder so that an aperture-containing wall portion thereof is interposed between said first electrode means and said second electrode means and controllably rotating said cylinder; said masking means being adapted to be removable for change in font, advancing means to advance a dielectric charge-retentive medium between said wall portion of said cylinder and said second electrode means; pulse means connected with each of said first substantially cylindrical first electrodes and said second electrode means for applying between selected ones of said first electrodes and said second electrode means controlled electrical pulses to produce between said first and said second electrode means electric fields to produce in the said ambient atmosphere nondisruptive ionizing electrical discharges, delimited by the said masking means, between said first electrode means and a dielectric charge-retentive medium advanced by said advancing means, to form on such a medium, at selected locations determined by which of said first cylindrical electrodes are pulsed of a group of possible selected locations determined by all of the first electrodes which may be pulsed, electric charge patterns similar in shape to the interposed aperture of said masking means; control means to control and synchronize the operation of said mounting and rotating means, said advancing means, and said pulse means to cause a said discharge to occur from said first electrode means when the aperture of a symbol to be recorded is interposed between said first and second electrode means, and the said advancing means has advanced between said first and said second electrode means an area of such record medium whereon such said symbol is to be recorded.

References Cited by the Examiner UNITED STATES PATENTS March 5, 1959.

BERNARD KONIOK, Primary Examiner. ROBERT H. ROSE, ROBERT SEGAL, Examiners.

W GARNER, V. P. CANNEY, Assistant Examiners, 

1. IN AN ELECTROSTATIC RECORDING PAGE PRINTER, THE COMBINATION COMPRISING: A RECORD MEDIUM STORE; MEANS FOR ADVANCING A RECORD MEDIUM HAVING A CHARGE-RETENTIVE OBVERSE FROM THE SAID STORE TOWARD A PRINTING STATION, THE SAID PRINTING STATION COMPRISING DISCHARGE ELECTRODE MEANS COMPRISING INDIVIDUAL ELECTRODES AND BACKING ELECTRODE MEANS ALIGNED WITH AND IN PROXIMITY TO SAID DISCHARGE ELECTRODE MEANS TO FORM A GAP FOR RECEIVING SAID RECORD MEDIUM BETWEEN SAID DISCHARGE AND BACK ELECTRODE MEANS FOR ESTABLISHING ELECTRIC CHARGES UPON THE OBVERSE OF SAID RECORD MEDIUM; DATA SOURCE AND CONTROL MEANS FOR APPLYING TO SAID DISCHARGE ELECTRODE MEANS ELECTRICAL PULSES SELECTIVELY IN ACCORDANCE WITH DATA FROM DATA SOURCE WHEREIN SAID PULSES ARE OF MAGNITUDE AND DURATION SUCH THAT SAID ELECTRIC CHARGES ARE ESTABLISHED ON SAID RECORD MEDIUM DURING A SHORT DURATION SUBSTANTIALLY OF THE ORDER OF THE PULSE WIDTH AND THE DISCHARGE IS TERMINATED IN A TIME PERIOD OF THE ORDER OF WITHIN A MICROSECOND; DEVELOPING AND FIXING MEANS FOR RENDERING THE DISTRIBUTION OF SAID ELECTRIC CHARGES ON SAID RECORD MEDIUM PERMANENTLY VISIBLE; APERTURED MASK MEANS MOVABLY INTERPOSED BETWEEN SAID INDIVIDUAL ELECTRODES OF SAID DISCHARGE ELECTRODE MEANS AND SAID RECORD MEDIUM SO TO SHAPE THE DISCHARGE FROM SAID DISCHARGE ELECTRODE MEANS AS TO PRODUCE ON SAID RECORD MEDIUM DISTRIBUTIONS OF ELECTRIC CHARGES APPROXIMATELY SIMILAR IN SHAPE TO THE APERTURES OF SAID APERTURED MASK MEANS; MEANS TO MAINTAIN SAID MASK MEANS AT A POTENTIAL TO FACILITATE GOOD DISCHARGE INTERMEDIATE THE POTENTIAL BETWEEN SAID INDIVIDUAL ELECTRODES OF SAID DISCHARGE ELECTRODE MEANS WHEN DISCHARGE OCCURS BUT SUFFICIENTLY APART FROM SAID LAST-NAMED POTENTIAL OF SAID INDIVIDUAL ELECTRODE MEANS SO THAT SAID MASK MEANS WILL NOT DISCHARGE TO SAID RECORD MEDIUM AND SUFFICIENTLY NEAR GROUND POTENTIAL SUCH THAT SAID MASK MEANS WILL NOT TEND TO CAPTURE THE CHARGES FROM SAID INDIVIDUAL ELECTRODES OF SAID DISCHARGE ELECTRODE AND PREVENT THEM FROM REACHING SAID RECORD MEDIUM. 